Mail Archives: geda-user/2013/08/20/11:55:15
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Hello All,
I'm trying to understand the VHDL back-end of gnetlist (and writing a
tutorial in the process).
If I include some symbols from the vhdl library and run netlist I get a
vhdl file with a component and the correct definitions:
(pin : in Std_Logic) if the "pintype" is defined as IN in the symbol.
So far so good.
However if I want pins to showup in my top-level ENTRY declaration I
need to include the "ipad-1.sym" or "opad-1.sym" in my design.
When I include the "ipad-1.sym" I get a symbol with a big OUT printed
inside it. This OUT is the result of the pintype definition inside the
symbol, its set to OUT (pintype=OUT). Now the fun begins, if I run
gnetlist I get a (pin : in Std_Logic) definition in my ENTRY
declaration. Even if pintype is set to OUT in the symbol the back-end
insists on making it an input type port signal.
Apparently the VHDL backend of gnetlist looks at the device attribute
(set to IPAD) to determine the direction of the port signal and not the
pintype attribute as it does with symbols.
Can anyone explain to me why? What is the design philosophy behind this?
Thanks and regards,
Robert.
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Hello All,<br>
<br>
I'm trying to understand the VHDL back-end of gnetlist (and writing
a tutorial in the process).<br>
If I include some symbols from the vhdl library and run netlist I
get a vhdl file with a component and the correct definitions:<br>
(pin : in Std_Logic) if the "pintype" is defined as IN in the
symbol.<br>
So far so good.<br>
However if I want pins to showup in my top-level ENTRY declaration I
need to include the "ipad-1.sym" or "opad-1.sym" in my design.<br>
When I include the "ipad-1.sym" I get a symbol with a big OUT
printed inside it. This OUT is the result of the pintype definition
inside the symbol, its set to OUT (pintype=OUT). Now the fun begins,
if I run gnetlist I get a (pin : in Std_Logic) definition in my
ENTRY declaration. Even if pintype is set to OUT in the symbol the
back-end insists on making it an input type port signal.<br>
Apparently the VHDL backend of gnetlist
looks at the device attribute (set to IPAD) to determine the
direction of the
port signal and not the pintype attribute as it does with symbols.
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Can anyone explain to me why? What is the design philosophy behind
this?<br>
<br>
Thanks and regards,<br>
Robert.<br>
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